Entoptic Phenomena

What entoptic image is created by LASIK?

Physiologic halos

2) Physiologic halos

Physiologic rings are dim halos seen around lights, this is caused by chromatic aberrations. -Size varies with wavelength of light, blue is the smallest

Polyopia and corneal tattoos

Polyopia- seeing multiple images -can be caused by holes/tears in the iris. -Treatment includes possible corneal tattoo to cover/block the hole, thus returning the pupil to the only entrance window.

What is vitreous syneresis

the process of vitreous liquefaction & condensation liquefaction = water starts to collect in pockets condensation = -water pockets break down gel => collagen fibril aggregate (ie. condense) into FLOATERS

How are retinal hemorrhages and posterior vitreous detachments similar?

-Both only seen when conditions change -Both visible because they are close to the retina, unlike lens or corneal issues. - Can be grossly monitored by patient using the purkinje tree

List the 8 entoptic phenomenon discussed in lecture?

1) Corneal Mosaic 2) Physiologic Halos 3) Vitreous floaters 4) Retinal Phosphenes 5) Purkinje tree 6) Blue field phenomenon 7) Blue retinal arcs 8) Haidinger brush/Maxwell spot

What do ganglion cells cause as a side effect?

1.2 million ganglion cells at birth -Packed into a small area between the fovea and the ONH -Causes the incoming light to be polarized

What are some floaters that the Dr can see but not the patient?

Asteroid hyalosis (pictured) or anterior uveitis

Glassblowers Cataract

Cataract caused by intense exposure to infrared radiation. -This is common in people who work with high temperature materials like glassblowing, metal workers, or blacksmiths. -Can be mitigated with protective eye wear.

Why don't patients see their cataracts like a shadow or image of some sort?

Cataract is diffuse and scatters light -Image will be dimmed and VA's will decrease -An image can be seen with the pinhole technique

3) Vitreous floaters

Caused by detachment of the vitreous form the optic nerve head. -Creates Weiss's ring -Eventually happens to everyone if they live long enough -Usually far enough away from the retina and lens that they can be treated with laser vitreolysis

What can we use the blue field phenomenon to monitor?

Clinically significant macular edema -There shouldn't be any of these little white spots showing up in the foveal avascular zone because there aren't any vessels there! -Shown to be the capillary loops of the inner nuclear/outer plexiform layers

Which type of entoptic phenomenon is caused by a harmless vitreous detachment? Which is caused by an emergency retinal detachment?

Floaters In retinal detachments you see a ton of sudden onset floaters that may move when you are not moving.

What corneal irregularities can be seen with the pinhole technique?

Fuchs dystrophy- folds appear as horizontal bands across the cornea Excessive oil or mucus in the tear film look like blobs with dark rings around them moving with blinks Contact lens wear- can cause shallow ridges in Bowman's layer to arise, visible when stained with NaFl

Which entoptic phenomenon can be used to diagnose eccentric fixation in strabismic amblyopia?

Haidinger brush

How can we use the purkinje tree technique to monitor diabetic retinopathy?

If the patient holds still and moves a pen light in front of the eyes, whey will be able to see floaters and hemorrhages in their vision that is otherwise unnoticed.

What is the use of the MPOD?

It tells us the levels of photopigment in the back of the eye This allows us to assess the health of the macula, and can be an early warning sign for the risk of AMD. A good MPOD is useful for protecting the fovea from blue light A good MPOD is also useful for things like night driving, glare, and seeing in bright light.

Other than glassblower's cataract, what pathology can IR radiation cause in the eye?

Lens exfoliation (lamellar delamination) -The anterior capsule of the lens thickens and eventually separates from the inner layers, extending into the anterior chamber. -Extremely similar to glassblowers cataracts

What does MPOD stand for?

Macular Pigment Optical Density

8) Haidinger brush

Made possible by using a spinning polarized target. -Seen in the visual field of the macula -Enhanced with a cobalt blue filter

Which entoptic phenomenon can be used by an observant patient to monitor glaucoma?

Maxwell spot or Haidinger brush

You can see chromatic aberrations around pinpoints of light, such as looking at stars, without having cataracts, so it must be from a healthy lens, so what is causing it?

Natural features of the lens, such as irregularities in the y-sutures, are the likely culprit to scattering light. -The pinhole technique used for observing the corneal mosaic can also be used to look at corneal opacities.

Negative dysphotopsias

Occur following cataract surgery The IOL can have a flat edge, which will mitigate the risk of posterior capsule opacification. -However, this can cause light refraction that causes shadows in the temporal aspect of the patients vision.

5) Purkinje tree- what is it and why do we not see it all the time?

Our visual system recognizes the retinal vasculature in front of the photoreceptors. -We don't normally see it because most sources of light are relatively stationary and we are moving, but if you are stationary and the light source moves quickly (like in slit lamp) you will see your purkinje tree.

DDX for physiologic halos

Pathological halos! From edematous cornea Contact overwearing Corneal scarring Cataracts

Focus Question: Which entoptic phenomena can help a patient monitor vascular disease like diabetic retinopathy?

Purkinje Tree

What is the premacular bursa?

Refers to the vitreous just anterior to the macula. -As we age, our vitreous loses the jelly like consistency and becomes more liquid. -This causes floaters which cast a shadow on the macula -The premacular bursa tends to liquefy first, meaning the shadows are cast on our central vision. -A harmless aspect of aging.

How does the MPOD work?

Relies on Heterochromatic Flicker Photometry Alternating flickering of blue and green LED, changing frequency and luminescence of the lights. The Xeanthanin will absorb blue, transmit green. Green starts out brighter than blue, and then green becomes less bright and blue becomes brighter. Overall brightness output stays the same. After each change, the frequency of flicker starts high (60Hz) and decreases (5Hz) so patient presses button when they see the flicker.

What are some pathological events that cause floaters?

Retinal tear/detachment- causes sudden onset, innumerable floaters. Emergency! Retinal hemorrhage- New, large spider-shaped floaters

6) Blue Field (sheerer) phenomenon

The blue light moving dot effect -Thought that the blue light is absorbed by the white blood cells in the retinal vasculature and so we see the moving dots with little tails. -Theoretically could be a sign of leukemia or neutropenia if the patient notices it more readily, although I question that.

1) Corneal endothelial mosaic

The endothelium of the cornea makes a hexagonal pattern on the back of the cornea. This pattern can be seen when you: -Set a 01.mm pinhole at the spectacle plane (17mm from cornea) -Backlight the pinhole -You will be able to see your tear film and possibly any irregularities in the cornea. -Tear film will be the little moving bits.

7) Blue retinal arcs

The nerve fiber layer also causes a phenomenon of blue arcs. - Longer wavelength of light is better for seeing -In a dark room, a red light source held parallel to the NFL will work -The arcs are dim gray in the dark, blue in the light (?) -Blue arcs move from fixation point to the blind spot -Works better if you look just off target -Monocular phenomenon

How can we use the haidinger brush in retinal diseases?

The nerve fiber layer is oriented in such a manner that it absorbs some polarized light, especially blue light -This means that if the patient has issues such as the macular edema, the haidinger brush will disappear from time to time. -Can tell us about disease that is not discernible with BIO!

How does the anatomy of the retina affect the blue arcs?

The nerve fiber layer runs in arcs from the ONH to the fovea. -Respects the midline. -Arcs seem to follow the ganglion cell fibers. -Lateral inhibition likely plays a role in the development of these arcs.

When do patients usually see their vitreous floaters?

They need to be looking at a bright ganzfeld. -Such as when doing visual fields or looking at the blue sky -They must be relatively close to the retina to cause a Penumbra (shadow) - They are very difficult for the Dr. to see

Why would a cortical cataract likely show up in the inferonasal lens?

This type of cataract is usually affected by UV exposure. -This means parts of the eye tend to be more protected by features like the nose or the brow, except the inferior-nasal area.

What is the clinical significance of the Haidinger brush for strabismus?

Used in eccentric fixation in strabismic patients -Since it is seen with the macula, if the are not fixating with the macula, they will see the brush in an off target space. -Can train them to move their eye to bring the macula (the brush) on target.

Scanning Laser Polarimetry

Using polarized light to measure the thickness of the nerve fiber layer over the retina. Used to assess glaucoma Ex. GDx Polarimetry

What is an Entoptic image?

Visual perceptions that are produced or influenced by native structures in your own eyes.

What causes the blue sky entoptic phenomenon?

We look at a ganzfeld and see little floaty bits. These are the white blood cells floating through out retinal arteries.

What is the deal with corneal tattoos?

When a scar forms on the cornea, it is often translucent. This causes irregularities in the light, reduces contrast, and results in entoptic images, can be problematic. -So they tattoo the scar to mimic the iris, thus the brain learns to stop paying attention to it. Reduces symptoms.

What is Maxwell's spot

When looking at a diffuse flickering blue light, we will see a Reddish circle surrounded by a white halo, then a blue halo. This is due to the absorption of the blue light by the yellow pigmented Xanthophyll pigments in the macula (lutein and zeaxanthin) So you don't get to see the blue light when you foveate on the flickering light.

4) Retinal pressure phosphenes

When we add pressure to the globe, it increases the IOP. This places pressure on the retina, causing the neurons to fire. -Perceived as points of light, flashes and such -Unique in that it is the only entoptic image that doesn't require an actual light source. -Many believe this is actually witchcraft.

Moore's lightning streaks are what? caused by?

vertical flashes of light - usually in the periphery. -Caused by vitreous detachment, which is not a problem. -If the patient only sees them when they move, most likely a harmless vitreous detachment. -If they see them when they are not moving, could be a retinal detachment! -Either way, dilate and confirm!

Teichopsia

visual blurring and colours associated with migraines AKA Forification spectrum or Widmastatten patterns